Dualsense battery voltage and battery life

[Squeck]

Hi!

I started refurbishing consoles and controllers in my spare time, and I'm having a hard time understanding when a Dualsense battery needs to be replaced. From what I understand, a brand new controller is around 3.8V, but what about a used one at 3.6V? Is it still good? I'm wondering when a battery gets too low for reasonable play time.

Thanks